Abstract
BackgroundPosterior lumbar fusion is a widely accepted surgical technique; however, it has been related to the possibility of paraspinal muscle atrophy after surgery. We investigated 1-year postoperative changes in paraspinal muscle volume using a simple formula applicable to magnetic resonance imaging (MRI) or computed tomography (CT) images.MethodsPatients with degenerative lumbar spinal stenosis who underwent posterior interbody fusion (PLIF) at the L4/5 level in the period from May 2010 to June 2017 were enrolled in this study. Radiologic parameters were measured using MRI or CT images which were taken before surgery and at 1 year after surgery. The volume of the paraspinal muscles was calculated using a simple formula which was derived from the formula for calculating the volume of truncated elliptic cones.ResultsA total of 40 patients were included; 24 were analyzed using MRI and 16 were analyzed using CT. The mean age of the patients was 59.6 ± 12.1 years and 32 (80.5%) were female. When comparing the preoperative and 1-year-postoperative images, multifidus muscle (MF) reduction was consistently observed in the MRI and CT groups, right and left (p = 0.003, p < 0.001, p = 0.005 and p < 0.001, respectively). In the erector spinae (ES) group, decrease in muscle volume was observed in the right-sided muscles of the CT group (p < 0.001), but no significant change was observed in the MRI group. The psoas muscle showed no significant change after 1 year. Conversely, regression analysis showed a negative correlation between MF muscle volume loss and age in the MRI group (right and left, p = 0.002 and p = 0.015, respectively), that is, the younger the age, the greater loss of muscle mass.ConclusionAfter the posterior lumbar fusion, the volume of the MF muscles was markedly decreased, and the degree of decrease was apparent in the MRI. The volume of the ES muscles, which are located relatively laterally, also tended to decrease at 1 year after surgery.
Highlights
Posterior lumbar fusion is a widely accepted surgical technique; it has been related to the possibility of paraspinal muscle atrophy after surgery
There was no significant difference in gender distribution, mean age, mean body mass index (BMI) and the measured preoperative volume of paraspinal muscles between the magnetic resonance imaging (MRI) group and the computed tomography (CT) group (Table 1)
The muscle volume measured 1 year after surgery in the right-sided multifidus muscle (MF) was smaller in the MRI group (p = 0.034) and that measured in the bilateral erector spinae muscles (ES) was smaller in the CT group
Summary
Posterior lumbar fusion is a widely accepted surgical technique; it has been related to the possibility of paraspinal muscle atrophy after surgery. Posterior lumbar fusion surgery is a widely accepted surgical technique in the treatment of lumbar spinal stenosis. This procedure is known to have several disadvantages, one of which is the postoperative atrophy of the paraspinal muscles [2,3,4,5,6]. Most previous studies explored the effects of posterior lumbar fusion surgery on the paraspinal muscles by quantitative analysis of magnetic resonance imaging (MRI) or computed tomography (CT) images using specific software [4, 5, 9,10,11,12]. The accuracy of the cross-section seems to be limited
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